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Merge pull request #240 from SixLabors/js/lru-cache-fixes
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Allow runtime physical deletion of cached images
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@JimBobSquarePants
JimBobSquarePants authored Mar 22, 2022
2 parents 21a6bc1 + 8bfe51f commit f91c093
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Showing 2 changed files with 52 additions and 24 deletions.
7 changes: 5 additions & 2 deletions src/ImageSharp.Web/Middleware/ImageContext.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,9 +86,12 @@ internal enum PreconditionState
}

/// <summary>
/// Returns the current HTTP request display url.
/// Returns the current HTTP image request display url.
/// </summary>
/// <returns>The. </returns>
/// <returns>
/// The combined components of the image request URL in a fully un-escaped form (except
/// for the QueryString) suitable only for display.
/// </returns>
public string GetDisplayUrl() => this.request.GetDisplayUrl();

/// <summary>
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69 changes: 47 additions & 22 deletions src/ImageSharp.Web/Middleware/ImageSharpMiddleware.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using Microsoft.IO;
Expand Down Expand Up @@ -184,12 +185,14 @@ public ImageSharpMiddleware(
/// <summary>
/// Performs operations upon the current request.
/// </summary>
/// <param name="context">The current HTTP request context.</param>
/// <param name="httpContext">The current HTTP request context.</param>
/// <returns>The <see cref="Task"/>.</returns>
public async Task Invoke(HttpContext context)
public Task Invoke(HttpContext httpContext) => this.Invoke(httpContext, false);

private async Task Invoke(HttpContext httpContext, bool retry)
{
// We expect to get concrete collection type which removes virtual dispatch concerns and enumerator allocations
CommandCollection commands = this.requestParser.ParseRequestCommands(context);
CommandCollection commands = this.requestParser.ParseRequestCommands(httpContext);

if (commands.Count > 0)
{
Expand All @@ -209,44 +212,44 @@ public async Task Invoke(HttpContext context)
}

await this.options.OnParseCommandsAsync.Invoke(
new ImageCommandContext(context, commands, this.commandParser, this.parserCulture));
new ImageCommandContext(httpContext, commands, this.commandParser, this.parserCulture));

// Get the correct service for the request
IImageProvider provider = null;
foreach (IImageProvider resolver in this.providers)
{
if (resolver.Match(context))
if (resolver.Match(httpContext))
{
provider = resolver;
break;
}
}

if ((commands.Count == 0 && provider?.ProcessingBehavior != ProcessingBehavior.All)
|| provider?.IsValidRequest(context) != true)
|| provider?.IsValidRequest(httpContext) != true)
{
// Nothing to do. call the next delegate/middleware in the pipeline
await this.next(context);
await this.next(httpContext);
return;
}

IImageResolver sourceImageResolver = await provider.GetAsync(context);
IImageResolver sourceImageResolver = await provider.GetAsync(httpContext);

if (sourceImageResolver is null)
{
// Log the error but let the pipeline handle the 404
// by calling the next delegate/middleware in the pipeline.
var imageContext = new ImageContext(context, this.options);
this.logger.LogImageResolveFailed(imageContext.GetDisplayUrl());
await this.next(context);
this.logger.LogImageResolveFailed(httpContext.Request.GetDisplayUrl());
await this.next(httpContext);
return;
}

await this.ProcessRequestAsync(
context,
httpContext,
sourceImageResolver,
new ImageContext(context, this.options),
commands);
new ImageContext(httpContext, this.options),
commands,
retry);
}

private void StripUnknownCommands(CommandCollection commands, int startAtIndex)
Expand All @@ -263,14 +266,15 @@ private void StripUnknownCommands(CommandCollection commands, int startAtIndex)
}

private async Task ProcessRequestAsync(
HttpContext context,
HttpContext httpContext,
IImageResolver sourceImageResolver,
ImageContext imageContext,
CommandCollection commands)
CommandCollection commands,
bool retry)
{
// Create a hashed cache key
string key = this.cacheHash.Create(
this.cacheKey.Create(context, commands),
this.cacheKey.Create(httpContext, commands),
this.options.CacheHashLength);

// Check the cache, if present, not out of date and not requiring an update
Expand All @@ -283,7 +287,7 @@ private async Task ProcessRequestAsync(

if (!readResult.IsNewOrUpdated)
{
await this.SendResponseAsync(imageContext, key, readResult.CacheImageMetadata, readResult.Resolver, null);
await this.SendResponseAsync(httpContext, imageContext, key, readResult.CacheImageMetadata, readResult.Resolver, null, retry);
return;
}

Expand Down Expand Up @@ -379,7 +383,7 @@ private async Task ProcessRequestAsync(
outStream.Position = 0;
string contentType = format.DefaultMimeType;
string extension = this.formatUtilities.GetExtensionFromContentType(contentType);
await this.options.OnProcessedAsync.Invoke(new ImageProcessingContext(context, outStream, commands, contentType, extension));
await this.options.OnProcessedAsync.Invoke(new ImageProcessingContext(httpContext, outStream, commands, contentType, extension));
outStream.Position = 0;

cachedImageMetadata = new ImageCacheMetadata(
Expand Down Expand Up @@ -409,7 +413,7 @@ private async Task ProcessRequestAsync(
}
}

await this.SendResponseAsync(imageContext, key, readResult.CacheImageMetadata, readResult.Resolver, outStream);
await this.SendResponseAsync(httpContext, imageContext, key, readResult.CacheImageMetadata, readResult.Resolver, outStream, retry);
}
finally
{
Expand Down Expand Up @@ -490,11 +494,13 @@ private async Task<ImageWorkerResult> IsNewOrUpdatedAsync(
}

private async Task SendResponseAsync(
HttpContext httpContext,
ImageContext imageContext,
string key,
ImageCacheMetadata metadata,
IImageCacheResolver cacheResolver,
Stream stream)
Stream stream,
bool retry)
{
imageContext.ComprehendRequestHeaders(metadata.CacheLastWriteTimeUtc, metadata.ContentLength);

Expand All @@ -518,10 +524,29 @@ private async Task SendResponseAsync(
}
else
{
using (Stream cacheStream = await cacheResolver.OpenReadAsync())
try
{
using Stream cacheStream = await cacheResolver.OpenReadAsync();
await imageContext.SendAsync(cacheStream, metadata);
}
catch (Exception ex)
{
if (!retry)
{
// The image has failed to be returned from the cache.
// This can happen if the cached image has been physically deleted but the item is still in the LRU cache.
// We'll retry running the request again in it's entirety. This ensures any changes to the source are tracked also.
CacheResolverLru.TryRemove(key);
await this.Invoke(httpContext);
return;
}

// We've already tried to run this request before.
// Log the error internally then rethrow.
// We don't call next here, the pipeline will automatically handle it
this.logger.LogImageProcessingFailed(imageContext.GetDisplayUrl(), ex);
throw;
}
}

return;
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